GB2254017A - Respirator filters - Google Patents

Respirator filters Download PDF

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Publication number
GB2254017A
GB2254017A GB9106462A GB9106462A GB2254017A GB 2254017 A GB2254017 A GB 2254017A GB 9106462 A GB9106462 A GB 9106462A GB 9106462 A GB9106462 A GB 9106462A GB 2254017 A GB2254017 A GB 2254017A
Authority
GB
United Kingdom
Prior art keywords
filter
canister
grid assembly
lid
wall
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9106462A
Other versions
GB2254017B (en
GB9106462D0 (en
Inventor
Nigel Robert Bonnett
Stephen Paul Furnell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sabre Safety Ltd
Original Assignee
Sabre Safety Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sabre Safety Ltd filed Critical Sabre Safety Ltd
Priority to GB9106462A priority Critical patent/GB2254017B/en
Publication of GB9106462D0 publication Critical patent/GB9106462D0/en
Publication of GB2254017A publication Critical patent/GB2254017A/en
Application granted granted Critical
Publication of GB2254017B publication Critical patent/GB2254017B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B01D53/0407—Constructional details of adsorbing systems
    • B01D53/0415—Beds in cartridges
    • A—HUMAN NECESSITIES
    • A62—LIFE-SAVING; FIRE-FIGHTING
    • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
    • A62B23/00—Filters for breathing-protection purposes
    • A62B23/02—Filters for breathing-protection purposes for respirators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/93—Toxic compounds not provided for in groups B01D2257/00 - B01D2257/708
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/45—Gas separation or purification devices adapted for specific applications
    • B01D2259/4541—Gas separation or purification devices adapted for specific applications for portable use, e.g. gas masks

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Respiratory Apparatuses And Protective Means (AREA)

Abstract

A respirator filter comprises a filter canister having a side wall 1 and includes a bed 3 of charcoal granules between grid assemblies 4 and 5. The filter is made by applying a compacting load to the bed 3 through the grid assembly 5 and, while the load is applied, securing the assembly 5 to the wall 2 of the canister by injecting a continuous bead 10 of hot melt adhesive into contact with both a circumferential rim of the grid assembly 5 and the wall 2 of the canister and allowing the adhesive to solidify. The solidified bead 10 seals the whole circumferential rim 11 of the grid assembly 5 to the wall 2 preventing any gases passing between the rim 11 of the grid assembly 5 and the wall 1 and so bypassing part of the bed 3. The solidified bead 10 also maintains the desired compaction of the bed 3 when the load is removed. An assembly comprising also a paper filter (26, Fig. 2) is described. <IMAGE>

Description

RESPIRATOR FILTERS This invention relates to respirator filters and more particularly to such filters which include a layer or bed of activated charcoal granules, or other absorbent granular or particulate material, for the removal of toxic gases.
In the manufacture of a respirator filter having a layer or bed of absorbent granular or particulate material, such as activated charcoal granules, the bed of charcoal granules is located in a canister between a pair of grid assemblies each of which usually comprises a circular apertured metal grille to which there are attached a support medium such as an open weave glass fibre mesh or scrim for preventing the charcoal granules from passing through the apertures of the metal grille, and a non-woven textile which may be a light weight viscose fabric for preventing charcoal dust from being carried in the breathing gas as this leaves the charcoal bed. The support medium and the dust filter are secured to the metal grille by bending over an edge of the metal grille to hold the other two components against the metal grille in a single grid assembly.The term "grid assembly" is used herein to denote an assembly of an apertured grille, a support medium such as an openweave glass fibre mesh and a dust filter such as a non-woven textile.
In order to ensure that the granules are held firmly in place and the resistance to air flow through the bed of charcoal granules is controlled, the charcoal granules are compacted under a predetermined known load and held under that load between two grid assemblies. In the manufacture of respirator filters having a metal canister the desired compaction of the bed of charcoal granules has been achieved by placing the charcoal granules in the canister on top of a first grid assembly, placing a second grid assembly on top of the granules, applying the load to the second grid assembly to compact the charcoal granules to the desired degree, and then swaging the metal canister to form a ring which holds the second grid assembly in the position where the desired compaction of the bed of charcoal granules is maintained, and which also seals the grid assembly against the metal wall of the canister so that gas cannot pass between the grid assembly and the wall of the canister.
This method cannot however be used when the respirator filter canister is made of plastics material.
The upper grid assembly may be located permanently in a plastics canister by ultrasonic welding in a method corresponding to that used on a metal canister, the ultrasonic welding being in place of the metal swaging. However the use of ultrasonic welding in this context is not an attractive proposition.
A method suitable for use in a respirator filter comprising a plastics canister and a bed of charcoal granules has been to utilize a closure element for the canister, which closure element has a cylindrical flange located within the canister housing and serving during assembly of the closure element onto the canister housing to cause the upper or second grid assembly to compress the charcoal granules to the desired extent and retain them in such compressed condition. However this method is dependent on secure fixing of the canister lid as well as on very accurate measurement of the quantity of charcoal granules and a very precise selection of the granule size, if the desired compaction of the charcoal granules is to be obtained.
In accordance with the present invention there is provided a method of making a respirator filter which comprises a filter canister having a substantially cylindrical wall of plastics material and a bed of absorbent granular material retained between lower and upper grid assemblies within the canister, the method including the steps of applying a desired compacting load to the bed of absorbent granular material through the upper grid assembly and, while the desired compacting load is applied, securing the upper grid assembly to the wall of the filter canister by injecting a hot melt adhesive into contact with both a circumferential rim of the upper grid assembly and the wall of the filter canister and allowing the hot melt adhesive to solidify, whereby the upper grid assembly maintains the desired compaction of the bed of absorbent granular material when the applied load is removed.
Preferably, the hot melt adhesive is caused to form a continuous bead which seals the whole circumferential rim of the upper grid assembly to the wall of the filter canister.
The bead of hot melt adhesive should be a shallow bead and in particular the inner edge of the bead of hot melt adhesive should not be higher than a plane containing the uppermost parts of the upper grid assembly. The hot melt adhesive is thus prevented from getting on the surface of the upper grid assembly and affecting the flow of filtered gas through the upper grid assembly. When the respirator filter is a combination filter, for example an NBC filter, the filter canister will contain a pleated paper filter as well as the bed of absorbent granular material.
The pleated paper filter is positioned in the filter canister between the upper grid assembly and the lid which closes the filter canister.
In a method according to the present invention for making such a combination respiratory filter the method includes the further steps of locating a pleated paper filter into a space between the upper grid assembly and a lid of the filter canister by spinning an assembly comprising the filter canister supported on the lid with a lip of the lid engaging the wall of the canister, the pleated paper filter supported within the lid, and liquid polyurethane within the lid, whereby the polyurethane is caused to flow outwardly of the lid and upwardly over the junction between the lip of the lid and the wall of the canister and into contact with the solidified hot melt adhesive.
The filter canister and the hot melt adhesive used must both be non-reactive with chemical gases which are to be filtered during their passage through the filter canister and must be unaffected by changes in temperature within a range from -400C to +800C.
The material of the hot melt adhesive must be compatible with the material of the filter canister, should have a cure time of the order of 15 to 30 seconds and should set rigid.
Advantageously, the filter canister and lid are made from a polyamide material, preferably Nylon, and the hot melt adhesive is a polyamide-based plastics material.
Conveniently, the lower grid assembly is an interference fit with the filter canister, said interference fit locking the lower grid assembly into position and providing a seal between the lower grid assembly and the wall of the filter canister.
Further in accordance with the present invention there is provided a respirator filter which comprises a filter canister having a substantially cylindrical wall, a first grid assembly located in the canister, a bed of absorbent granular material supported on the first grid assembly, a second grid assembly in contact with an upper surface of the bed of absorbent granular material, and a bead of a solidified hot melt adhesive material sealing the edge of the upper grid assembly to the wall of the filter canister and holding the upper grid assembly in position to maintain the bed of absorbent granular material between the first and second grid assemblies under a predetermined degree of compaction.
In one preferred embodiment of the present invention the respirator filter further comprises a lid having a substantially cylindrical wall engaging the wall of the filter canister, a pleated paper filter located within the lid between said lid and the upper grid assembly, and a film of plastics material such as polyurethane sealing the pleated paper filter to the wall of the lid, overlying the junction between the wall of the lid and the wall of the canister and thereby bonding the lid to the canister, and said film of plastics material contacting and at least partially overlying the bead of solidified hot melt adhesive material.
The present invention will be further understood from the following detailed description of a preferred embodiment thereof which is made, by way of example, with reference to the accompanying drawings in which Figure 1 is an enlarged cross-sectional view of a part of a filter respirator comprising a bed of charcoal granules compacted between lower and upper grid assemblies, the upper grid assembly being held in position by a method in accordance with the present invention, and Figure 2 is a side view in part section of an NBC filter respirator made by a method in accordance with the present invention.
Referring to Figure 1 of the accompanying drawings, there is shown in cross-section a part of a filter canister which is part of a substantially cylindrical side wall 1 and base 2 of a filter canister made of a Nylon material. The filter canister contains a bed 3 of charcoal granules which are retained under a desired compacting pressure between a lower grid assembly 4 and an upper grid assembly 5. Both the upper and lower grid assemblies are conventional grid assemblies comprising an apertured metal grille 6, an open-weave glass fibre sheet 7 and a lightweight non-woven viscose fabric 8.
The lower grid assembly 4 is an interference fit within the substantially cylindrical wall 1 of the filter canister. Because the filter canister is made by an injection moulding process, the wall 1 thereof is not absolutely cylindrical but makes an angle of approximately 10 with the vertical, the narrowest part of the filter canister being near its base 2. The lower grid assembly 4, being an interference fit, penetrates into the wall 1 of the filter canister near the base 2 as shown at 9. The penetration of the rim of the lower grid assembly 4 into the wall 1 of the filter canister provides a seal preventing gases passing between the lower grid assembly 4 and the wall 1 and also locates the lower grid assembly 4 in desired position.
In making the filter according to the invention and illustrated in Figure 1 of the accompanying drawings, a desired quantity of charcoal granules is placed on the lower grid assembly 4 to form a bed 3 of charcoal granules of a desired thickness. The upper grid assembly 5 is then introduced into the filter canister and placed on top of the bed 3 of charcoal granules which are then compressed by a known load applied to the upper grid assembly 5.
While the known load is applied to the upper grid assembly 5, thus producing a desired specific density of the charcoal granules, a hot melt adhesive, preferably a polyamide based plastics adhesive, is injected through a nozzle of diameter of the order of 1 mm into contact with both the rim 11 of the upper grid assembly 5 and the wall 1 of the filter canister.
The filter canister is rotated through 3600 while the hot melt adhesive is injected so that a continuous shallow bead 10 is formed contacting the rim 11 and the wall 1 around the whole circumference of the upper grid assembly 5. As the hot melt adhesive sets or cures within a time of the order of 15 to 30 seconds, the bead 10 of hot melt adhesive secures the upper grid assembly 5 in the position in the filter canister where the bed 3 of charcoal granules is compressed to the desired specific density and the the bead 10 also forms a seal preventing any gases passing between the rim 11 of the upper grid assembly 5 and the wall 1 of the filter canister.
The inner edge of the bead 10 has a height well below the plane of the upper surface of the upper grid assembly 5.
The filter canister containing the bed 3 of charcoal granules with the upper grid assembly located in the manner described with reference to Figure 1 constitutes a sub-assembly which is capable of being handled without affecting the density of the charcoal granules constituting the filter bed.
Referring now to Figure 2 of the accompanying drawings, there is shown in part section an NBC respirator filter which comprises a filter canister 21 and a lid 22, a bed 23 of charcoal granules compressed between upper and lower grid assemblies 24 and 25 and a pleated paper filter 26 positioned between the upper grid assembly 25 and the lid 22.
In manufacturing the NBC respirator filter of Figure 2 the bed 23 of charcoal granules is compressed to a desired specific density of the charcoal and secured in that position by the method described with reference to Figure 1 so that a bead 27 of solidified hot melt adhesive locates the upper grid assembly 25 in position by sealing the upper grid assembly 25 against the wall 21 of the filter canister. As shown in Figure 2, the bead 27 is so shallow that no part of the bead 27 extends up to the level of the plane of the uppermost parts of the upper grid assembly 25.
In the next stage of manufacture the pleated paper filter 26 is placed in the inverted lid 22 and the lid 22 and the sub-assembly of the filter canister 21 containing the bed 23 of charcoal granules between the grid assemblies 24 and 25 are snapped together to the position shown in Figure 2 with the wall of the open end of the filter canister 21 a snap fit over an upturned lip 28 of the lid 22. The assembly of canister 21 and lid 22 is then placed in an inverted position on a spinning rig having a raised spigot, the upper end of which locates inside the lid 22, at the centre of the intake of the lid 22, and below the pleated paper filter 26. A deposit of liquid polyurethane has been placed on a dished surface at the upper end of the raised spigot before the assembly of canister 21 and lid 22 is placed on the spinning rig. The assembly is therefore inverted from the position shown in Figure 2 but the pleated paper filter is loose and the lid and canister are not bonded together. The pleated paper filter 26 is supported in the lid above the liquid polyurethane.
The assembly is then spun so that the liquid polyurethane is caused to move away from the centre of the lid 22 and rise up the lip 28 of the lid 22 into contact with the edges of the pleated paper filter 26 and also the portion of the inner surface of the wall 21 of the filter canister as far as the bead 27. The polyurethane sets during the spinning operation as a film 29 which seals the pleated paper filter 26 to the lip 28 of the lid 22, to the wall 21 and to the bead 27, while also bonding the lid 22 and the wall 21 of the canister firmly together. In contacting and overlying the bead 27 the polyurethane provides an additional seal preventing passage of gases through any crack which might appear in the bead 27.
The method of the present invention may be used in conjunction with an upper grid assembly having a circumferential lip of a deformable resilient material, the circumferential lip being deformed by the wall of the filter canister so that the deformed resilient lip forms a continuous seal against the wall of the canister. The bead 27, which then secures the deformed circumferential lip of the upper grid assembly to the wall of the filter canister, need not then be continuous, although it is preferred that it be continuous. A method of making a filter canister using an upper grid assembly having a circumferential lip of deformable resilient material, and a respirator filter incorporating such an upper grid assembly are described and claimed in our co-pending Application No. of even date herewith.

Claims (11)

1. A method of making a respirator filter which comprises a filter canister having a substantially cylindrical wall of plastics material and a bed of absorbent granular material retained between lower and upper grid assemblies within the canister, the method including the steps of applying a desired compacting load to the bed of absorbent granular material through the upper grid assembly and, while the desired compacting load is applied, securing the upper grid assembly to the wall of the filter canister by injecting a hot melt adhesive into contact with both a circumferential rim of the upper grid assembly and the wall of the filter canister and allowing the hot melt adhesive to solidify, whereby the upper grid assembly maintains the desired compaction of the bed of absorbent granular material when the applied load is removed.
2. A method according to Claim 1 wherein the hot melt adhesive is caused to form a continuous bead which seals the whole circumferential rim of the upper grid assembly to the wall of the filter canister.
3. A method according to Claim 2 wherein the inner edge of the bead of hot melt adhesive is not higher than a plane containing the uppermost parts of the upper grid assembly.
4. A method according to any one of the preceding Claims which includes the further steps of locating a pleated paper filter into a space between the upper grid assembly and a lid of the filter canister by spinning an assembly comprising the filter canister supported on the lid with a lip of the lid engaging the wall of the canister, the pleated paper filter supported within the lid, and liquid polyurethane within the lid, whereby the polyurethane is caused to flow radially outwardly against the lip of the lid and upwardly over the junction between the lip of the lid and the wall of the canister and into contact with the solidified hot melt adhesive.
5. A method according to any one of the preceding Claims wherein the filter canister is made from a polyamide plastics material and the injected hot melt adhesive is a polyamide-based plastics adhesive.
6. A method according to any one of the preceding claims wherein the lower grid assembly is an interference fit with the filter canister, said interference fit locking the lower grid assembly into position and providing a seal between the lower grid assembly and the wall of the filter canister.
7. A respirator filter which comprises a filter canister having a substantially cylindrical wall, a first grid assembly located in the canister, a bed of absorbent granular material supported on the first grid assembly, a second grid assembly in contact with an upper surface of the bed of absorbent granular material, and a bead of a solidified hot melt adhesive material sealing the edge of the upper grid assembly to the wall of the filter canister and holding the upper grid assembly in position to maintain the bed of absorbent granular material between the first and second grid assemblies under a predetermined degree of compaction.
8. A respiratory filter according to Claim 7 wherein the filter canister is made from polyamide plastics material and the bead is a solidified polyamide-based plastics adhesive.
9. A respiratory filter according to Claim 7 or Claim 8 which further comprises a lid having a substantially cylindrical lip engaging the wall of the filter canister, a pleated paper filter located within the lid between said lid and the upper grid assembly, and a film of plastics material sealing the pleated paper filter to the lip of the lid, overlying the junction between the lip of the lid and the wall of the canister and thereby bonding the lid to the canister, and said film of plastics material contacting and at least partially overlying the bead of solidified hot melt adhesive material.
10. A method of making a respiratory filter substantially as hereinbefore described with reference to the accompanying drawings.
11. A respiratory filter substantially as hereinbefore described with reference to the accompanying drawings.
GB9106462A 1991-03-26 1991-03-26 Respirator filters Expired - Lifetime GB2254017B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9106462A GB2254017B (en) 1991-03-26 1991-03-26 Respirator filters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9106462A GB2254017B (en) 1991-03-26 1991-03-26 Respirator filters

Publications (3)

Publication Number Publication Date
GB9106462D0 GB9106462D0 (en) 1991-05-15
GB2254017A true GB2254017A (en) 1992-09-30
GB2254017B GB2254017B (en) 1994-05-11

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Family Applications (1)

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GB9106462A Expired - Lifetime GB2254017B (en) 1991-03-26 1991-03-26 Respirator filters

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5478377A (en) * 1994-07-22 1995-12-26 The United States Of America As Represented By The Secretary Of The Army Filter for a respiratory device
WO2006096284A1 (en) * 2005-03-03 2006-09-14 3M Innovative Properties Company Conformal filter cartridges and methods
WO2008081489A1 (en) * 2007-01-05 2008-07-10 Officine Meccaniche Galli S.R.L. Nbc filter
WO2013008226A1 (en) * 2011-07-12 2013-01-17 Yarok Bair Protection Industries Ltd. Carbon filter device and air filter apparatus
GB2583165A (en) * 2019-01-25 2020-10-21 Aquaten Ltd Apparatus and method for capturing airborne contaminants

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4714486A (en) * 1985-07-03 1987-12-22 Her Majesty The Queen In Right Of Canada Automated production of canisters
GB2223423A (en) * 1988-09-22 1990-04-11 Canada Minister Defence Compression seal canister

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4714486A (en) * 1985-07-03 1987-12-22 Her Majesty The Queen In Right Of Canada Automated production of canisters
GB2223423A (en) * 1988-09-22 1990-04-11 Canada Minister Defence Compression seal canister

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5478377A (en) * 1994-07-22 1995-12-26 The United States Of America As Represented By The Secretary Of The Army Filter for a respiratory device
WO2006096284A1 (en) * 2005-03-03 2006-09-14 3M Innovative Properties Company Conformal filter cartridges and methods
US7419526B2 (en) 2005-03-03 2008-09-02 3M Innovative Properties Company Conformal filter cartridges and methods
CN101132835B (en) * 2005-03-03 2012-01-11 3M创新有限公司 Conformal filter cartridges and manufacturing methods thereof
WO2008081489A1 (en) * 2007-01-05 2008-07-10 Officine Meccaniche Galli S.R.L. Nbc filter
WO2013008226A1 (en) * 2011-07-12 2013-01-17 Yarok Bair Protection Industries Ltd. Carbon filter device and air filter apparatus
GB2583165A (en) * 2019-01-25 2020-10-21 Aquaten Ltd Apparatus and method for capturing airborne contaminants

Also Published As

Publication number Publication date
GB2254017B (en) 1994-05-11
GB9106462D0 (en) 1991-05-15

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732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PE20 Patent expired after termination of 20 years

Expiry date: 20110325